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The realization of Kitaev spin liquid, where spins on a honeycomb lattice are coupled ferromagnetically by bond-dependent anisotropic interactions, has been a sought-after dream. 5d iridium oxides α-Li 2 IrO 3 and α-Na 2 IrO 3 with a honeycomb lattice of J eff = 1/2 moments recently emerged as a possible materialization. Strong signature of Kitaev physics, however, was not captured. Here we report the discovery of a complex iridium oxide β-Li 2 IrO 3 with J eff = 1/2 moments on "hyper-honeycomb" lattice, a three-dimensional analogue of honeycomb lattice. A positive Curie-Weiss temperature θ CW ~ 40 K indicated dominant ferromagnetic interactions among J eff = 1/2 moments in β-Li 2 IrO 3 . A magnetic ordering with a small entropy change was observed at T c = 38 K, which, with the application of magnetic field of only 3 T, changed to a fully polarized state of J eff = 1/2 moments. Those results imply that hyper-honeycomb β-Li 2 IrO 3 is located in the vicinity to a Kitaev spin liquid.

We present near edge X-ray absorption spectra of manganese oxides at the Mn L2,3, Mn K, and O K edges to investigate the relative sensitivity of the edges to bonding and structure. Collectively, the spectra probe local electronic structure and intermediate range crystal structure. Spin independent full multiple scattering calculations of the Mn K edge give good agreement with data above threshold and qualitatively reproduce the prepeak that is observed for each compound. We show that the apparent prepeak for MnO is not due to p−d hybridization at the Mn atom (in accordance with symmetry principles) or quadrupolar transitions but originates from multiple scattering within the fifth shell. We present spin dependent multiple scattering calculations of the O K edge and show that this edge allows for a more direct description of the 3d states than either the Mn L edge or K edge prepeak, which are complicated by multiplet effects.